Herein, the authors produce Co-based (Co3 (PO4 )2 , Co3 O4 , and Co9 S8 ) electrocatalysts via pulsed laser ablation in liquid (PLAL) to explore the synergy of anion modulation on phase-selective active sites in the electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Co3 (PO4 )2 displays an ultralow overpotential of 230 mV at 10 mA cm-2 with 48.5 mV dec-1 Tafel slope that outperforms the state-of-the-art Ir/C in OER due to its high intrinsic activity. Meanwhile, Co9 S8 exhibits the highest HER performance known to the authors among the synthesized Co-based catalysts, showing the lowest overpotential of 361 mV at 10 mA cm-2 with 95.8 mV dec-1 Tafel slope in the alkaline medium and producing H2 gas with ≈500 mmol g-1 h-1 yield rate under -0.45 V versus RHE. The identified surface reactive intermediates over in situ electrochemical-Raman spectroscopy reveal that cobalt(hydr)oxides with higher oxidation states of Co-cation forming under oxidizing potentials on the electrode-electrolyte surface of Co3 (PO4 )2 facilitate the OER, while Co(OH)2 facilitate the HER. Notably, the fabricated two-electrode electrolyzers using Co3 (PO4 )2 , Co3 O4 , and Co9 S8 electrocatalysts deliver the cell potentials ≈2.01, 2.11, and 1.89 V, respectively, at 10 mA cm-2 . This work not only shows PLAL-synthesized electrocatalysts as promising candidates for water splitting, but also provides an underlying principle for advanced energy-conversion catalysts and beyond.

Unraveling the Synergy of Anion Modulation on Co Electrocatalysts by Pulsed Laser for Water Splitting: Intermediate Capturing by In Situ/Operando Raman Studies.

Fabrication of bismuth ferrite/graphitic carbon nitride/N-doped graphene quantum dots composite for high performance supercapacitors

Pulsed laser-driven green synthesis of trimetallic AuPtCu nanoalloys for formic acid electro-oxidation in acidic environment

Ligand-free monophasic CuPd alloys endows boosted reaction kinetics toward energy-efficient hydrogen fuel production paired with hydrazine oxidation

Cation modulation engineering is employed to tune the intrinsic activity and electronic structure of electrocatalysts for water electrolysis. Here, we designed two-dimensional cobalt–iron-layered double-hydroxide (CoFe-LDH) ultrathin nanosheets by pulsed laser ablation in an aqueous medium. The CoFe-LDH nanosheets exhibited abundant electrochemically active sites and a large surface area. The optimal Co0.5Fe0.5-LDH exhibited a low overpotential of 270 mV during half-cell oxygen evolution reactions (OERs), whereas Co0.25Fe0.75-LDH delivered 365 mV at 10 mA/cm2 during hydrogen evolution reactions (HERs). The bifunctional electrocatalyst exhibited an outstanding water electrolyzer performance at a cell voltage of ∼1.89 V at 10 mA/cm2 and admirable stability for long-run repetitive cycles. The synergistic effect between the modulated cations resulted in better conductivity, and the mass transfer facilitated the HER and OER. We demonstrated that this facile approach can facilitate the engineering of a highly stable and efficient electrode for renewable electrochemical energy conversion reactions. 

Dual-Cation-Coordinated CoFe-Layered Double-Hydroxide Nanosheets Using the Pulsed Laser Ablation Technique for Efficient Electrochemical Water Splitting: Mechanistic Screening by In Situ/Operando Raman and Density Functional Theory Calculations

Multiscale Design of 3d Metal–Organic Frameworks (M-Btc, M: Cu, Co, Ni) Via Plal Enabling Bifunctional Electrocatalysts for Robust Overall Water Splitting

Shankar Naik Shreyanka

Papers

Multiscale Design of 3d Metal–Organic Frameworks (M-Btc, M: Cu, Co, Ni) Via Plal Enabling Bifunctional Electrocatalysts for Robust Overall Water Splitting

Ligand-free monophasic CuPd alloys endows boosted reaction kinetics toward energy-efficient hydrogen fuel production paired with hydrazine oxidation